Twenty-nine patients at the Veterans Administration hospital in Pittsburgh have been diagnosed with Legionnaires' disease since January 2011, raising questions about the institution's safety practices.

Five of the cases "are known to have acquired the disease from the hospital," the VA said. Another eight were infected elsewhere, and the source of the infection in 16 cases cannot been determined.

The spate of illnesses has led relatives of two veterans who died after contracting the disease, a type of pneumonia, to blame the hospital.

CNN has learned that hospital officials knew they had a problem with the water system as far back as last December, but chose not to reveal that until a month ago.

That's when the hospital began turning off the water in parts of the hospital, staff and patients told CNN.